This invention relates generally to fiber optic acoustic sensors and particularly to fiber optic acoustic sensors for underwater use. Still more particularly, this invention relates to apparatus and methods for providing a hydrophone having a planar configuration.
The conventional method for the detection of acoustic pressures underwater is perormed by piezoelectric elements. Traditionally, ceramic elements and, more recently, electrically active polymer films have been employed. Associated with these transducers are the required electronics to amplify the signal prior to transmitting it along data-bus.
Conventional acoustic sensor are electrically active; and it is, therefore, necessary to supply power to the sensors. This tends to add weight, bulk, complexity, and cost to the system. In addition, if a breach should occur in the "wet end" sub-system, the hydrophone and associated electronics will be exposed to the underwater environment. This may cause the system to malfunction and ultimately fail. Further, piezoelectric systems have a limited acoustic sensitivity, are often sensitive to acceleration, and are prone to extraneous electromagnetic signal pickup. Additionally, the greater number of sensors that are needed for the detection of quieter acoustic signals, will increase the transmission bandwidth and associated bit which will intern limit the ultimate system performance.
Previous fiber optic acoustic sensors have a generally cylindrical configuration.